1. Field of the Invention
The present invention relates to an environment recognition device and an environment recognition method for recognizing a target object based or a luminance of the target object in a detection area.
2. Description of Related Art
Conventionally, a technique has been known that detects a target object such as an obstacle including a vehicle and a traffic light located in front of a subject vehicle for performing control to avoid collision with the detected target object and to maintain a safe distance between the subject vehicle and the preceding vehicle (for example, Japanese Patent No. 3349060 (Japanese Patent Application Laid-Open (JP-A) No. 10-283461).
Further, in such techniques, there is a technique that performs more advanced control. Specifically, it not only specifies a target object uniformly as a solid object, but further determines whether the detected target object is a preceding vehicle that is running at the same speed as the subject vehicle or a fixed object that does not move in this case, when the target object is detected by capturing an image of a detection area, it is necessary to extract (cut out) the target object from the captured image before specifying what the target object is.
For example, when the captured image is a color image, there may be a method for extracting, as a target object, a set of pixels having a same luminance (color).
However, when color or sizes of a character and a graphic, which axe displayed on a light-emitting traffic sign or a digital signage, are similar to those of a lighting portion of a traffic light, simply grouping the plural pixels having the similar color characteristics may cause the character and the graphic to be falsely recognized as the traffic light. Even if an indicator is larger than the lighting portion of the traffic light, a displayed character and a graphic are not always continuously drawn depending on a display mode of the indicator, and may be separately grouped. As a result, the character and the graphic are unlikely to be recognized as being displayed on the same substance. Accordingly, the inventor of the present application has developed a technique for further unifying grouped target objects according to conditions, and for example, distinguishing between a traffic light and a light-emitting traffic sign.
However, in this kind of technique, small light-emitting objects may be unified against the intention, and a specific object that is not originally desired to be recognized may be falsely recognized as a specific object. For example, multiple lights installed in a tunnel with a narrow interval are located in proximity in a captured image, and accordingly, the lights are of a size close to that of a traffic light, as a result of the above unifying technique. As a result, the lights may be falsely recognized as a traffic light.